论文部分内容阅读
对日本冲绳岛北部相同土壤条件下的琉球松纯林及其混交林的土壤氮素及有机碳素、地表凋落物量、枯枝落叶量以及土壤氮素矿化速率进行了比较研究。结果表明 ,琉球松纯林的地表凋落物层氮、碳平均贮量分别为133kg·hm- 2 和 7199kg·hm- 2 ,混交林则分别为 10 5kg·hm- 2 和 6 14 3kg·hm- 2 。然而 ,混交林地表 10cm矿质土层的氮、碳贮量则显著高于纯林 ,氮素比纯林多 4 93kg·hm- 2 ,碳素多 5 5 5 4kg·hm- 2 。在 30d的实验室培养实验中 ,混交林表层土壤的氮素矿化速率高于纯林 18% ;而且 ,混交林的落叶和土壤的碳氮比值亦明显低于松纯林。混交林土壤的年平均矿化氮素 (NH4+ +NO3- )浓度高于纯林 2 2 %。与松纯林相比 ,混交林通过枯枝落叶年平均氮素归还量多 4 3 7kg·hm- 2 ,碳素归还量多 16 5 5kg·hm- 2 。混交林具有较高的氮素归还量 ,主要是混交林的针叶含氮含量较高以及大量的高含氮量的阔叶落叶所致。上述结果充分说明针阔混交导致了林分氮素循环的变化。
Soil nitrogen and organic carbon, litterfall, litter amount and soil nitrogen mineralization rate under the same soil conditions in northern Okinawa, Japan were compared. The results showed that the average nitrogen and carbon storage of the litter in the pure Ryukyu pine forests were 133 kg · hm-2 and 7199 kg · hm-2, respectively, while the mixed forest was 105 kg · hm-2 and 6143 kg · hm- 2 . However, the N and C stocks in the 10 cm mineral layer on the surface of the mixed forest were significantly higher than those in the pure forest, with 4 93 kg · hm-2 more nitrogen and 554 kg · hm-2 more carbon than the pure forest. In the laboratory experiment of 30 days, the mineralization rate of nitrogen in surface soil of mixed forest was higher than that of pure forest by 18%. Moreover, the ratio of carbon and nitrogen in deciduous forest and soil in mixed forest was significantly lower than that in pure pine forest. The annual mean mineralized nitrogen (NH4 + + NO3-) concentration in mixed forest soil is higher than that of pure forest by 22%. Compared with the pure pine forest, the average annual nitrogen return through the litter exceeded 477 kg · hm-2, and the return of carbon was more than 165 kg · hm-2. Mixed forest with high nitrogen return, mainly mixed forest coniferous nitrogen content is high and a large number of high nitrogen content of broadleaf leaves. The above results fully demonstrated that the coniferous and broad-leaved hybrid led to changes in the nitrogen cycle of stands.